Food Biochemistry and Food Processing

4 Browning Reactions 91

found the corresponding Amadori compound in
spray-dried egg yolk powders and lecithin products
derived therefrom and proposed the Amadori com-
pound content of these products as a possible quality
criterion. Oak et al. (2002) detected the Amadori
compounds derived from glucose and lactose in sev-
eral processed foods with high amounts of carbohy-
drates and lipids such as infant formula, chocolate,
mayonnaise, milk, and soybean milk; of these, infant
formula contained the highest levels of Amadori-PEs.
However, these compounds were not detected in oth-
er foods due to differences in composition and the rel-
atively low temperatures used during the processing.
As an example, Figure 4.14 shows a scheme for
the formation of the Amadori compounds derived
from glucose and lactose with PE. Carbohydrates

react with the amino group of PE to form an unsta-

ble Schiff base, which undergoes an Amadori re-

arrangement to yield the stable PE-linked Amadori

product (Amadori-PE).

On the other hand, similar to proteins, phospho-

lipids such as PE and ethanolamine can react with

secondary products of lipid peroxidation such as

4,5-epoxyalkenals. Zamora and Hidalgo (2003b)

studied this reaction in model systems and charac-

terized different polymers responsible for brown

color and fluorescence development, confirming that

lipid oxidation products are able to react with

aminophospholipids in a manner analogous to their

reactions with protein amino groups; therefore, both

amino phospholipids and proteins might compete

for lipid oxidation products.

Figure 4.13.General pathways of pyrrole formation during polyunsaturated fatty acid oxidation (Zamora and Hidalgo

1995).